New Methodology Makes for Quicker Genetic ID of Japanese U.S. Termites

For several termite species that are responsible for structural damage in the United States, such as: For example, the rapid reticulitermes flavipes shown here, identification is a critical part of management efforts. A team of researchers has developed a faster ID method that uses a genetic tool called inter-simple sequence repeats. (Photo by Joseph Berger, Bugwood.org)

By Andrew Porterfield

Andrew Porterfield

Termites (genus Reticulitermes) are not only an expensive pest, but also play an important ecological role in the decomposition of cellulose material. Twelve species of termites are known in the United States, and the species responsible for structural damage cost Americans about $ 11 billion a year to control.

In the United States, four Reticulitermes species (R. flavipes, R. tibialis, R. virginicus, and R. hesperus) and one invasive species (Coptotermes formosanus) are responsible for almost all termite control efforts. Identifying the correct species in a structure is important for control because the insects have different colonies and different feeding areas. Identification is also important for ecological studies on termites (pest or non-pest) to weed large amounts of sample.

Identifying termites is not an easy task, however. Three current methods – morphology, cuticle hydrocarbon profiles, and genetic methods – all have their drawbacks. Morphological identification requires large samples of breeding or soldier sets, which are difficult to obtain. Cuticle hydrocarbon profiles can vary between colonies, making it more difficult to distinguish species. DNA sequencing is effective but time consuming and requires knowledge of molecular biology and computer science to analyze data.

Among several species of termite of the genus Reticulitermes found in the USA, four (R. flavipes, R. tibialis, R. virginicus and R. hesperus) together with the invasive species Coptotermes formosanus account for 90 percent of the termite control business. Rapid identification is an important part of the management effort, and a team of researchers has developed a new, faster ID method that uses a genetic tool called inter-simple sequence repeats. The areas (shaded) and sampling points (dots) of the reticulitermes termite species included in the study are shown here. (Image originally published in Janowiecki et al. 2021, Journal of Economic Entomology)

To solve this problem, researchers at Texas A&M University, the University of Arkansas, and BASF Corporation developed a simpler genetic method of identification that can distinguish five species of eastern termite within hours. Their findings were published this week in the Journal of Economic Entomology.

Mark Janowiecki, Ph.D., led the research during his PhD at Texas A&M and is now an entomologist with the New Orleans Mosquito, Termite and Rodent Control Board. He and his colleagues used a genetic tool called Inter-Simple Sequence Repeats (ISSR) to identify the termites. ISSRs are fragments of DNA (about 100 to 3,000 base pairs of nucleotides) that are located between identical “microsatellite” regions of DNA. These can provide a unique DNA “fingerprint” of a species.

The ISSR DNA is amplified from small sample sizes using the polymerase chain reaction (PCR). The technique is based on a primer (a small strip of DNA) that represents a complementary match to the microsatellite region. This makes the technique easier because no sequence data is needed for primer construction, and more precisely because ISSRs are found randomly in the genome.

“Our goal was to update previous methods … to identify subterranean termites using a simple tool that can be run concurrently with microsatellite genotyping analysis,” says Janowiecki. “At the time, another student in the department was working in our lab doing ISSRs to identify fly species. That’s why I decided to check whether this method is suitable for termites. I found a paper describing ISSR primers for other termite species and started testing them for these types of reticuliterms. “

Researchers examined several species of termites for 16S mitochondrial DNA (a specific segment of a ribosome in mitochondria that is generally less variable than other DNA) and examined 10 ISSR primers. Other termites from the western United States and Canada were also examined for possible species overlap.

One of the 10 ISSRs was found which contained species-specific fragments with sufficient variability to distinguish between species (R. flavipes, R. hageni, R. virginicus, R. tibialis and R. malletei). Although some species overlap was found, the researchers report that all five had “a diagnostic, species-specific fragment”.

The ISSR method can be completed in about 11 hours, versus 14 to 34 hours required for other genetic methods. However, the authors caution that the method may not work for all geographic regions. Some species of termites in the western United States and some invasive termites have ISSR fragments that are similar to eastern species, which can be confusing. “We screened other species and found that they had temporarily overlapping fragments with the focus species we included. To include all species, it might be possible to use multiple ISSRs, but at that point the ISSR method would lose its efficiency, ”says Janowiecki.

Andrew Porterfield is an author, editor, and communications consultant for academic institutions, corporations, and nonprofits in the life sciences. He frequently writes on agricultural issues for the Genetic Literacy Project. He lives in Camarillo, California. Follow him on Twitter @AMPorterfield or visit his Facebook page.

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